Add puzzle template to the Slack modal

[FionaDL]

Problem:

The puzzles are inconsistent in how they are structured. There was a template created to show how a puzzle should be structured (with code snippets), but the template only exists in the repo. It would be hard for a user to see that when they are using a Slack modal to submit puzzles.

AC:

• User has can see the template example in the Slack modal

[FionaDL]

Gelsey and I will take this issue on Tuesday